The currency in the United Kingdom is the British Pound or GBP (£). The United Kingdom does not use the Euro (€) as used in other European Union countries. It is unusual for any currency other than the pound to be accepted in shops or restaurants in the United Kingdom except for a few large shops in London or at the airport.
The most straightforward way to obtain cash is to withdraw it from ATM machines. These are easily accessible throughout Britain (if there is anywhere in your itinerary that does not have easy access to an ATM, we will let you know). Banks in the UK do not charge for the use of ATMs but your bank at home may charge a fee for withdrawing currency abroad. However, bank withdrawals tend to have a better rate of exchange than using currency exchange houses.
Almost all shops and restaurants in Britain accept payment by either debit or credit card. In some small shops or cafes there may be a minimum spend to pay by card, usually £5 or £10. Visa and Mastercard are the most widely accepted credit cards. Some businesses will accept American Express but it is not universal and there may sometimes be a fee.